Carbon monoxide toxicity: a case series

Obstructive Tracheal Necrosis in a Dog Secondary to Smoke Inhalation Injury-Case Report

A 4-year-old Siberian Husky mix was referred to the emergency service of the University of California Davis Veterinary Medical Teaching Hospital after being found unconscious in a housefire. Upon arrival, the dog was conscious and panting with normal breathing effort. The dog was initially treated with oxygen therapy to minimize the risk of carbon monoxide toxicosis. Progressive agitation with paroxysmal episodes of increased respiratory effort and increased upper airway sounds were noted ~48 h after presentation. Hypoxemia was then documented. Clinical signs continued to progress despite supportive measures, and five days after initial presentation mechanical ventilation was deemed indicated. Following anesthetic induction, endotracheal intubation was performed. Capnography and peak inspiratory pressures recorded on the mechanical ventilator were consistent with airway obstruction. Diffuse intraluminal tracheal obstruction with grossly necrotic tracheal tissue was confirmed using fiber optic tracheoscopy. The patient was humanely euthanized due to grave prognosis. At necropsy, the tracheal lumen was obstructed by sloughed, necrotic tracheal mucosa. This is the first report describing a severe delayed intrathoracic large airway complication secondary to smoke inhalation in a dog.

Pathology of carbon monoxide poisoning in two cats

Background

Carbon monoxide (CO), a common cause of poisoning in human beings has also been implicated in the death of animals. Though there are multiple studies on CO poisoning and relevant lethal blood COHb concentrations in humans, there are no reliable reports of diagnostic lethal carboxyhemoglobin percentage of saturation (COHb%) in cats. Additionally, due to shared housing environments, exposures to companion animals can be a surrogate for lethal exposures in human beings and provide valuable information in concurrent forensic investigations.

Case presentation

Two adult Singapura brown ticked cats were submitted to the California Animal Health and Food Safety Laboratory (CAHFS) for necropsy and diagnostic work-up. These animals were found dead along with their two deceased owners. Similar lesions were observed in both cats. At necropsy, gross lesions consisted of multifocal, large, irregular, bright red spots on the skin of the abdomen and the inner surface of ear pinnae, bright red muscles and blood. The carcasses, and tissues fixed in formalin retained the bright red discoloration for up to two weeks. Microscopic lesions included diffuse pulmonary congestion and edema, and multifocal intense basophilia of cardiomyocytes mostly affecting whole fibers or occasionally a portion of the fiber. Based on the clinical history,gross and microscopic changes, cyanide or carbon monoxide poisoning was suspected. Blood samples analyzed for carbon monoxide showed 57 and 41% carboxyhemoglobin COHb%. Muscle samples were negative for cyanide.

Conclusion

There are no established reference values for lethal COHb concentration in cats. The COHb % values detected in this case which fell within the lethal range reported for other species, along with the gross lesions and unique histological findings in the heart suggest a helpful criteria for diagnosis of CO intoxication associated death in cats. This case demonstrates that since pets share the same environment as human beings and often are a part of their activities, they can be useful adjuncts in potential forensic investigations to help solve human cases.

Successful outcome in a dog with neurological and respiratory signs following smoke inhalation

OBJECTIVE

To report the case management of a patient with smoke inhalation complicated by neurological impairment, carboxyhemoglobinemia, acute respiratory distress syndrome (ARDS), upper airway obstruction, aspiration pneumonia, and bacteremia.

CASE SUMMARY

A 1.5-year-old male intact Beagle presented shortly after being involved in a household fire. Upon arrival the dog was diagnosed with ARDS and demonstrated acute neurological signs (eg, obtundation and seizures). Treatment included mechanical ventilation, temporary tracheostomy, and intensive supportive care. During hospitalization, the dog suffered multiple complications including prolonged neurological abnormalities, aspiration pneumonia, and bacteremia. The dog recovered over a 16-day period.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first description of extensive management of a patient suffering both neurological and respiratory complication due to smoke inhalation, and details the steps that were taken to achieve a successful outcome.

Severe burn injury, burn shock, and smoke inhalation injury in small animals. Part 1: burn classification and pathophysiology

OBJECTIVE

To review the literature related to severe burn injury (SBI), burn shock, and smoke inhalation injury in domestic animals. Current animal- and human-based research and literature were evaluated to provide an overview of thermal burn classification and the pathophysiology of burn shock and smoke inhalation injury.

ETIOLOGY

Severe burn injury, burn shock, and smoke inhalation injury may be encountered as a result of thermal injury, radiation injury, chemical injury, or electrical injury.

DIAGNOSIS

Burns can be subdivided based on the amount of total body surface area (TBSA) involved and the depth of the burn. Local burn injuries involve <20% of the TBSA whereas SBI involves >20-30% of the TBSA. The modern burn classification system classifies burns by increasing depth: superficial, superficial partial-thickness, deep partial-thickness, and full-thickness.

SUMMARY

Local burn injury rarely leads to systemic illness whereas SBI leads to significant metabolic derangements that require immediate and intensive management. SBI results in a unique derangement of cardiovascular dysfunction known as "burn shock." The physiologic changes that occur with SBI can be divided into 2 distinct phases; the resuscitation phase and the hyperdynamic hypermetabolic phase. The resuscitation phase occurs immediately following SBI and lasts for approximately 24-72 hours. This period of hemodynamic instability is characterized by the release of inflammatory mediators, increased vascular permeability, reduced cardiac output, and edema formation. The hyperdynamic hypermetabolic phase begins approximately 3-5 days after injury. This phase is characterized by hyperdynamic circulation and an increased metabolic rate that can persist up to 24 months post burn injury in people.

Severe burn injury, burn shock, and smoke inhalation injury in small animals. Part 2: diagnosis, therapy, complications, and prognosis

OBJECTIVE

To review the evaluation and treatment of patients suffering from severe burn injury (SBI), burn shock, and smoke inhalation injury. Potential complications and prognosis associated with SBI are also discussed.

DIAGNOSIS

Diagnosis of burn injury and burn shock is based on patient history and clinical presentation. Superficial burn wounds may not be readily apparent for the first 48 h whereas more severe wounds will be evident at presentation. Patients are diagnosed with local or SBI by estimating total body surface area involved using the 'Rule of Nines' or the Lund-Browder chart adapted from the human literature.

THERAPY

Patients suffering from SBI require immediate and aggressive fluid therapy. Burn wounds require prompt cooling to prevent progressive tissue damage. Due to significant pain associated with burn wounds and therapeutic procedures, multimodal analgesia is recommended. Daily wound management including hydrotherapy, topical medications, and early wound excision and grafting is necessary with SBI.

COMPLICATIONS

There are numerous complications associated with SBI. The most common complications include infections, hypothermia, intra-abdominal hypertension, and abdominal compartment syndrome.

PROGNOSIS

The prognosis of SBI in domestic animals is unknown. Based on information derived from human literature, patients with SBI and concomitant smoke inhalation likely have a worse prognosis than those with SBI or smoke inhalation alone.

The association of physical examination abnormalities and carboxyhemoglobin concentrations in 21 dogs trapped in a kennel fire

OBJECTIVE

To evaluate physical examination findings and their association with carboxyhemoglobin (COHb) concentrations in 21 dogs that were exposed to smoke during a kennel fire.

SERIES SUMMARY

Twenty-one dogs were exposed to a kennel fire. Physical exam findings, presenting, and posttherapy COHb concentrations as well as therapeutic interventions were evaluated. COHb concentrations upon presentation were increased in all smoke inhalation exposed dogs. These dogs were compared to a small set of clinically normal staff-owned dogs who were not exposed to fire. Physical parameters significantly associated with higher COHb concentrations included lower body temperature, increased respiratory effort, abnormal respiratory auscultation, altered neurologic status, and length of hospital stay. Oxygen therapy resulted in a more rapid decline in COHb concentrations although 5 dogs still had mildly increased COHb concentrations 24-hour postadmission.

UNIQUE INFORMATION PROVIDED

This study describes the relationship of admitting clinical findings of dogs exposed to a kennel fire with their initial blood COHb concentrations. It also describes the resolution of increased COHb concentrations with use of oxygen therapy and hospitalization. Additionally, COHb concentrations for a control group of dogs was evaluated and compared to the dogs exposed to smoke inhalation.

Feline blood transfusions: A pinker shade of pale

PRACTICAL RELEVANCE

blood transfusions are a potentially life-saving procedure that are within the reach of most small animal practitioners. Only minimal equipment is required.

PATIENT GROUP

any cat with clinical signs attributable to a reduced red blood cell mass that is affecting oxygen transport (as a result of reduced packed cell volume or acute blood loss) is a potential candidate for a transfusion.

CLINICAL CHALLENGES

although the principles of transfusion medicine are not complicated, there can be fatal consequences if certain steps are omitted.

DIAGNOSTICS

blood typing kits and blood filters are readily available from veterinary wholesalers, laboratories and blood banking services.

EVIDENCE BASE

over the past three decades, a substantial body of clinical research and reports has built up covering feline blood types and transfusion medicine. This article draws on that research to provide clinical guidance aimed at all veterinarians in feline or small animal practice who either currently practise transfusion medicine or plan to do so.

Leukoencephalomalacia and Laminar Neuronal Necrosis Following Smoke Inhalation in a Dog

Acute respiratory and neurologic disease after smoke inhalation are well documented, but human patients may also develop delayed-onset neurologic symptoms associated with leukoencephalomalacia after exposure to smoke or carbon monoxide. In this case, a dog developed progressive neurologic signs 6 days after rescue from an apartment fire. At necropsy 9 days after smoke inhalation, leukoencephalomalacia of the central cerebral white matter was accompanied by laminar necrosis of cerebrocortical neurons. This is the first report of delayed posthypoxic leukoencephalopathy in a nonhuman animal.